Andy,
The support for DEL among browsers is weak, STRIKE is useful in the current situations.
I suggest you can let your client use the style builder to apply the inline style to the content.
Hello World - Use DEL
Hello World - Use STRIKE
Hello World - Use inline style
asp.net Chat http://cutesoft.net/ASP.NET+Chat/default.aspx
Web Messenger: http://cutesoft.net/Web-Messenger/default.aspx
asp.net wysiwyg editor: http://cutesoft.net/ASP.NET+WYSIWYG+Editor/default.aspx
asp wysiwyg html editor: http://cutesoft.net/ASP
asp.net Image Gallery: http://cutesoft.net/ASP.NET+Image+Gallery/default.aspx
Live Support: http://cutesoft.net/live-support/default.aspx